Electrically-operated injection molding machine

Abstract

A precision injection molding apparatus is provided with servo mechanisms in various portions of the apparatus including a resin injection portion to provide precise feedback control of resin weighing, blending, and injection of weighed and blended resin into a die cavity between closed dies, a die opening and closing portion to provide precise feedback control for driving a movable die from a spaced position into a closed position relative to a fixed die to provide the die cavity, a gate cutting portion to provide precise feedback control of gate cutting, a molding ejecting portion to provide precise feedback control of ejecting a formed molding and a molding removing portion to provide precise feedback control for removing the molding from between opened dies. Because servo mechanisms are used, there is no variation in repetitive response accuracy of motion and speed of operation can be increased in terms of cycle speeds without loss of accuracy.

What is claimed is:  
     
       1. A precision injection molding machine, comprising: 
       a resin injection portion including apparatus configured to provide precise feedback control of a resin servo mechanism providing resin weighing, blending and injection of weighed and blended resin into a die cavity between closed dies;  
       a die opening and closing portion including apparatus configured to provide precise feedback control of a die servo mechanism driving a movable die into a closed position relative to a fixed die to provide the die cavity between closed dies and to a spaced position relative to the fixed die to open the dies;  
       a gate cutting portion including apparatus configured to provide precise feedback control of a gate cutting servo mechanism providing gate cutting after resin injection into the die cavity is completed;  
       a molding ejecting portion including apparatus configured to provide precise feedback control of a molding ejecting servo mechanism providing ejection of a formed molding after the dies are open; and  
       a molding removing portion including apparatus configured to provide precise feedback control of a molding removing servo mechanism configured to remove the molding from between opened dies.  
     
     
       2. The injection molding machine according to claim  1 , wherein the gate cutting servo mechanism further comprises, 
       a gate cutting screw mechanism,  
       a gate cutting member connected to said gate cutting screw mechanism and configured to perform reciprocating movements through the movable die, and  
       a gate cutting servo motor configured to cause said reciprocating movements of said gate cutting member via the gate cutting screw mechanism; and  
       wherein the molding ejecting servo mechanism further comprises,  
       an ejection screw mechanism,  
       an ejection member connected to said ejection screw mechanism and configured to perform reciprocating movements through the movable die, and  
       a molding ejecting servo motor configured to cause said reciprocating movements of the ejection member via the ejection screw mechanism; and  
       further wherein a screw shaft of the gate cutting screw mechanism and a center ejecting bar of the ejection screw mechanism are arranged on a same axis, the center ejecting bar is inserted in the screw shaft,  
       and the gate cutting screw mechanism is located closer to the dies than the ejection screw mechanism.  
     
     
       3. The injection molding machine according to claim  1 , wherein the molding removing servo mechanism is driven by a servo motor, 
       the molding ejecting servo mechanism includes an ejection screw mechanism driven by a molding ejection servo motor,  
       and the molding removing servo mechanism is configured to remove the molding from between the opened dies under a condition with little time loss or free of time loss in response to a controller electrically controlling a timing for ejecting said molding by the molding ejecting servo mechanism and a timing for removing the molding by said molding or moving servo and mechanism.  
     
     
       4. The injection molding machine according to claim  1  or  3 , wherein the molding ejecting servo mechanism includes spaced apart ejection members configured to move through the movable die. 
     
     
       5. The injection molding machine according to claim  1 , further comprising: 
       a hollow gate cutting member configured for sliding movement through the movable die as part of said gate cutting servo mechanism;  
       an ejection member provided as part of the molding ejecting servo mechanism and configured for insertion in and slidable movement through the hollow gate cutting member;  
       a gate cutting drive nut portion configured to provide forward and reverse sliding movement to the hollow gate cutting member, said eject nut portion being attached to the threaded portion on an outer side of a screw shaft which is a part of the gate cutting member;  
       an eject nut portion configured to provide forward and reverse sliding movement to the ejection member, said eject nut portion being attached to a threaded portion of a center eject bar which is a part of said ejection member;  
       a pulley configured to be driven by a servo motor provided to simultaneously rotate the gate cutting drive nut portion and the eject nut portion,  
       wherein the gate cutting drive nut portion and the eject nut portion are inversely threaded relative to each other.  
     
     
       6. An injection molding machine comprising: 
       a movable die plate mounting a movable die;  
       a housing with a toggle mechanism;  
       a pressure sensor placed between said movable die plate and said housing and configured to sense a reactive force arising from resin in a die cavity between a fixed die and the movable die;  
       a toggle servo motor configured to drive said toggle mechanism to move said movable die plate mounting and said movable die so that said movable die engages the fixed die;  
       a servo controller configured to feedback control resin injection pressure into the die cavity,  
       the feedback controller also providing feedback control of a die clamping force between the fixed die and the movable die and position control of said movable die based on data from said pressure sensor indicating relative pressure on the resin in said cavity.  
     
     
       7. The injection molding machine according to claim  6 , further comprising: 
       an ejection mechanism configured to eject a molding, said ejection mechanism including spaced apart ejection members passing through the pressure sensor, the die plate, and the movable die.  
     
     
       8. The injection molding machine according to claim  6 , further comprising: 
       a hollow gate cutting member configured for slidable movement through a movable die and movable die plate;  
       an ejection member configured for slidable movement in the hollow gate cutting member;  
       a gate cutting drive nut portion configured to provide forward and reverse slidable movement to the hollow gate cutting member, said gate cutting drive nut being attached to a threaded portion on an outer side of a screw shaft which is part of the hollow gate cutting member;  
       an eject nut portion configured to provide forward and reverse slidable movement to the ejection member, said eject nut portion being attached to a threaded portion of a center eject bar which is a part of said ejection member;  
       a pulley configured to be driven by a servo motor provided to simultaneously rotate the gate cutting drive nut portion and the eject nut portion, wherein the gate cutting drive nut portion and the eject nut portion are inversely threaded relative to each other.